The present invention relates in general to non lethal kinetic energy projectiles, and in particular to spin-stabilized non lethal kinetic energy projectiles.
In general, previous non lethal kinetic energy projectiles have been designed for relatively short range encounters, usually in the 7 meter to 15 meter range. To achieve a high probability of hit on a specific human target, at these ranges, a high degree of ballistic accuracy is not necessary. It is quite possible to obtain this level of performance from an aerodynamically unstable projectile. However, hit probability diminishes rapidly when attempting to engage beyond these ranges. This is due to inconsistent aerodynamic forces generated by unstable, and possibly inconsistent, projectile shapes.
Existing designs include fabric bags which are filled with lead shot. These are sewn into a square or a round pancake-shaped geometry, then folded to fit into an appropriate cartridge case over a gas seal. After gun launch, these "bean-bags" are not physically constrained, resulting in flight body shapes which vary over the trajectory. As such, the resulting shape, and aerodynamic forces generated by that shape, are extremely inconsistent. These discrepancies cause consequential changes in both the drag and lift forces, producing significant deviations from the intended trajectory. Furthermore, these bean bags typically assume a high drag shape during flight, rapidly losing velocity and energy.
Another category of non lethal projectile consists of a single, or multiple, right circular cylinder(s). Generically referred to as "rubber bullets", these items are typically constructed of hard rubber, foam, plastic, or wood. It is possible to achieve aerodynamic stability with such a projectile, but only if the proper spin rate is imparted. However, the majority of these devices are launched from a smoothbore tube, and therefore, tumble in flight. In addition, they have a flat forward face which once again results in a high drag shape.
In order to achieve the desired level of performance, a spin-stabilized projectile with a low drag shape is preferred. This would allow the projectile to reach a range significantly greater than current state-of-the-art non lethal projectiles, without losing considerable velocity, while maintaining a predictable flight path.
The method of propulsion typically employed for previous designs included a charge of black powder which was ignited by a percussion primer. The reduced mass and low velocity required for non lethal projectile applications restricts the working pressure to a level that modern smokeless powders will not deflagrate (burn) consistently. This generally produces large deviations in muzzle velocity and often leaves partially consumed powder in the cartridge case and weapon bore. The one attractive characteristic of black powder is its propensity to burn consistently at lower pressure, providing excellent performance for non lethal munitions. However, the burning of black powder also produces heavy, corrosive residue. This residue can quickly accumulate to the point of adversely affecting weapon performance. In order to avoid a degradation in effectiveness, the weapon barrel requires frequent cleaning. In addition, the corrosive products attack metallic components. Therefore, especially for military applications, the disadvantages of black powder can outweigh the benefits.
The present invention exhibits several advantages over previous designs. First, it is a projectile designed to impart a non lethal impact to a human target from a wide range of distances. This specific design utilizes spin-stabilization, in combination with a low drag shape. These characteristics allow the projectile to maintain low dispersion and retain adequate terminal velocity to remain effective at extended ranges. Second, it contains a compliant nose which compresses to absorb energy upon impact. This technique reduces the likelihood of skin abrasion, laceration, skeletal or organ damage by more evenly distributing the force over the impact site.
The nose material also modifies the impulsive force, by increasing the time and decreasing the magnitude over which the impact energy is transferred to the target. This is an advantage over designs which employ non-compliant materials. Third, it is propelled by a modern smokeless propellant which is burned at a higher pressure and controllably vented into the weapon chamber to work upon the projectile base. This "high-low" technique provides much greater consistency in muzzle velocity when compared to a conventional single-stage propulsion system producing similar interior ballistics. Lastly, this cartridge is designed to be fired from several existing U.S. military weapons with no modifications.